Determinants of healthcare utilization and costs in COPD patients: first longitudinal results from the German COPD cohort COSYCONET

Figures & data

Table 1 Characteristics of the study population

	GOLD classification					All Participants^a (n=1904)		p-value
	Grade 1 (n=168)	Grade 2 (n=719)	Grade 3 (n=568)	Grade 4 (n=135)	Grade unclassified (n=301)
	Baseline					Baseline	Visit 3
Age (years)	65.8 (8.6)	65.5 (8.0)	64.9 (7.6)	62.3 (7.2)	65.5 (9.1)	65.1 (8.1)	66.8 (8.1)	<0.0001^c
% Age <55 years	10.1	9.3	9.3	14.1	14.3	10.6	7.7	<0.0001^b
% Age 55–64 years	28.0	33.0	37.3	49.6	28.6	34.1	28.8	<0.0001^b
% Age 65–74 years	48.8	46.0	44.9	31.9	41.9	44.4	46.7	0.0085^b
% Age >74 years	13.1	11.7	8.5	4.4	15.3	10.9	16.6	<0.0001^b
% Males	62.5	60.5	60.2	63.7	52.5	59.5
Lung Function
FEV1 (liter)	2.62 (0.6)	1.85 (0.5)	1.20 (0.3)	0.76 (0.2)	2.30 (0.7)	1.72 (0.7)	1.64 (0.7)	<0.0001^c
FVC (liter)	4.12 (0.9)	3.31 (0.8)	2.68 (0.8)	2.07 (0.6)	2.99 (0.9)	3.05 (1.0)	2.95 (1.0)	<0.0001^c
FEV1/FVC	64.0 (4.1)	56.6 (7.9)	46.3 (8.8)	38.9 (9.6)	76.8 (5.1)	56.1 (13.5)	55.2 (13.8)	<0.0001^c
Smoking Status
% Never smoker	6.6	6.0	6.0	6.7	11.6	7.0	7.0	.
% Former smoker	66.1	64.8	73.4	75.6	64.8	68.3	71.6	<0.0001^b
% Current smoker	27.4	29.2	20.6	17.8	23.6	24.7	21.4	<0.0001^b
BMI (kg/m^2)	26.8 (4.8)	27.5 (4.9)	26.5 (5.2)	24.5 (4.9)	29.5 (5.6)	27.2 (5.2)	27.1 (5.4)	0.0044^c
% Underweight (BMI <18.5)	1.8	1.8	3.9	6.7	1.0	2.6	3.4	0.0053^b
% Normal weight (18.5≤ BMI <25)	36.3	31.7	38.3	54.8	21.3	34.1	35.1	0.1670^b
% Overweight (25≤ BMI <30)	41.1	38.3	36.0	27.4	34.9	36.5	35.8	0.4347^b
% Obese (BMI ≥30)	20.8	28.2	21.9	11.1	42.9	26.8	25.8	0.0563^b
Exacerbation^d
% No exacerbation	66.7	52.0	37.4	30.4	55.8	48.2	54.2	<0.0001^b
% Mild exacerbation	3.0	6.8	3.0	4.4	4.7	4.8	3.5	0.0366^b
% Moderate exacerbation	22.6	29.2	33.5	26.7	27.6	29.4	29.4	0.9381^b
% Severe exacerbation	7.7	12.0	26.1	38.5	12.0	17.6	12.9	<0.0001^b
Symptoms
% with presence of cough	43.7	42.4	43.7	43.3	51.8	44.5	43.1	0.2323^b
% with presence of sputum production	44.6	43.1	46.5	46.3	50.7	45.8	45.9	0.8930^b
% with presence of dyspnea	19.3	30.4	58.4	78.2	30.7	41.3	43.5	0.0268^b
Comorbidity count	4.1 (2.6)	3.9 (2.6)	3.8 (2.5)	3.1 (2.2)	4.6 (3.0)	3.9 (2.6)	4.7 (2.9)	<0.0001^c
% Comorbidity count >3	51.8	49.0	48.4	38.5	59.1	49.9	70.5	<0.0001^b

Notes: Data are mean (standard deviation) or percentage. Means and percentages relate to participants with valid data for that particular variable. ^a13 participants have missing GOLD grades at baseline, but are included under “All participants”. ^bp-value based on McNemar test. ^cp-value based on Wilcoxon Signed Rank test.^dExacerbation history in previous 12 months.

Table 2 Unadjusted healthcare utilization and resulting mean annual direct costs (€), at baseline and 18 month follow-up visit (Visit 3)

	GOLD grade 1 (n=168)		GOLD grade 2 (n=719)		GOLD grade 3 (n=568)		GOLD grade 4 (n=135)		grade unclassified (n=301)		All participants^a (n=1,904)		p-value
	Baseline	Visit 3	Baseline	Visit 3	Baseline	Visit 3	Baseline	Visit 3	Baseline	Visit 3	Baseline	Visit 3
Healthcare utilization
Outpatient services^d (3 months)
% User	95.2	92.2	94.3	92.5	97.5	93.2	97.0	96.2	95.7	92.9	95.7	92.9	<0.0001^b
Total number of visits	6.6 (6.5)	5.8 (6.3)	6.1 (5.4)	5.5 (5.1)	6.5 (5.6)	5.9 (7.3)	5.9 (4.5)	5.2 (5.4)	6.5 (5.2)	6.6 (7.6)	6.3 (5.5)	5.8 (6.4)	<0.0001^c
Inpatient services (12 months)
% User	28.1	27.3	32.6	32.0	41.6	36.6	50.8	51.5	35.1	31.3	36.6	34.1	0.0645^b
Number of hospital days	2.9 (6.2)	2.7 (6.5)	3.6 (8.9)	4.8 (13.0)	6.7 (13.3)	6.5 (14.2)	9.4 (17.3)	9.5 (13.6)	4.0 (13.1)	4.5 (12.2)	4.9 (11.7)	5.4 (12.9)	0.6211^c
Prescribed medication (7 days)
% User	95.8	96.4	96.9	97.8	99.5	98.2	98.5	100.0	93.0	93.4	97.1	97.2	0.6961^b
Number of prescribed drugs	4.8 (3.2)	5.0 (3.3)	5.3 (3.0)	5.7 (3.3)	6.6 (3.2)	6.8 (3.4)	6.7 (3.3)	7.2 (3.8)	5.3 (3.8)	5.6 (4.1)	5.7 (3.3)	6.0 (3.6)	<0.0001^c
Direct costs (12 months), Euro (2012 values)
Outpatient costs	832 (809)	771 (952)	828 (773)	732 (712)	897 (769)	809 (1133)	829 (646)	724 (667)	840 (728)	840 (981)	850 (758)	776 (918)	<0.0001^c
Inpatient costs	1,689 (3,638)	1,589 (3,826)	2,113 (5,235)	2,842 (7,633)	3,923 (7,862)	3,827 (8,372)	5,559 (10,198)	5,576 (8,018)	2,379 (7,694)	2,633 (7,185)	2,895 (6,916)	3,169 (7,595)	0.5746^c
Medication costs	2,241 (5,097)	1,974 (2,304)	2,057 (2,133)	2,539 (5,090)	2,793 (3,450)	2,901 (3,454)	2,901 (3,550)	2,844 (2,016)	1,836 (2,203)	2,355 (4,725)	2,311 (3,060)	2,580 (4,207)	0.0458^c
Other costs^e	376 (1,022)	384 (1,318)	443 (1,074)	507 (1,318)	681 (1,246)	525 (1,138)	738 (1,375)	747 (1,226)	465 (1,092)	535 (1,079)	533 (1,153)	520 (1,220)	0.0885^c
Total direct costs	5,362 (7,724)	4,841 (6,258)	5,553 (6,394)	6,573 (10,322)	8,300 (9,677)	8,091 (11,012)	10,172 (11,846)	9,734 (9,032)	5,821 (9,170)	6,616 (10,834)	6,739 (8,629)	7,091 (10,274)	0.1016^c

Notes: Numbers represent participants in each GOLD grade category assigned at baseline. Data are mean (standard deviation) or percentage. Means and percentages relate to participants with valid data for that particular variable. ^a13 participants have missing GOLD grades at baseline, but are included under “All participants”. ^bp-value based on McNemar test. ^cp-value based on Wilcoxon Signed Rank test. ^dIncludes general practitioner, specialist, and outpatient hospital care.

Table 3 Effect of COPD and baseline characteristics on future annual direct costs

Covariate		Outpatient costs^a	Inpatient costs	Medication costs	Other costs^b	Total Direct costs
		n=1,819	n=1,813	n=1,804	n=1,782	n=1,731
Intercept		433.29 [302.40–620.85]	457.74 [194.46–1,077.47]	1,203.80 [987.53–1,467.44]	189.71 [89.72–401.16]	2,301.23 [1,758.09–3,012.17]
COPD GOLD	grade 1	ref.	ref.	ref.	ref.	ref.
	grade 2	0.99 [0.82–1.20]	1.48 [0.93–2.36]	1.08 [0.97–1.20]	1.37 [0.90–2.08]	1.24 [1.07–1.43]
	grade 3	1.00 [0.81–1.22]	1.49 [0.89–2.47]	1.23 [1.10–1.38]	1.23 [0.79–1.93]	1.27 [1.09–1.48]
	grade 4	0.94 [0.71 1.24]	2.39 [1.22–4.69]	1.23 [1.05–1.43]	1.74 [0.97–3.14]	1.57 [1.27–1.93]
	grade unclassified	1.03 [0.83–1.29]	1.17 [0.69–1.97]	0.96 [0.84–1.08]	1.61 [1.00–2.58]	1.14 [0.96–1.34]
Age (years)	<55	ref.	ref.	ref.	ref.	ref.
	55–64	1.04 [0.86–1.25]	1.30 [0.83–2.02]	1.02 [0.92–1.14]	1.00 [0.67–1.48]	1.09 [0.95–1.26]
	65–74	1.04 [0.86–1.26]	1.90 [1.22–2.95]	1.09 [0.98–1.21]	1.02 [0.68–1.51]	1.24 [1.07–1.42]
	>74	1.11 [0.87–1.40]	1.52 [0.87–2.65]	1.13 [0.99–1.30]	0.90 [0.54–1.49]	1.20 [1.01–1.43]
Sex	male	ref.	ref.	ref.	ref.	ref.
	female	1.03 [0.92–1.15]	0.83 [0.63–1.08]	0.99 [0.93–1.05]	1.17 [0.92–1.49]	0.95 [0.87–1.03]
Education	basic	ref.	ref.	ref.	ref.	ref.
	secondary	1.10 [0.98–1.24]	1.05 [0.79–1.41]	0.98 [0.92–1.05]	1.06 [0.82–1.38]	1.03 [0.94–1.13]
	higher	0.96 [0.83–1.11]	0.78 [0.55–1.10]	0.94 [0.87–1.02]	1.01 [0.74–1.37]	0.90 [0.80–1.00]
Smoking status	never smoker	ref.	ref.	ref.	ref.	ref.
	smoker	1.06 [0.83–1.34]	1.62 [0.92–2.85]	1.03 [0.91–1.17]	0.90 [0.55–1.48]	1.19 [1.00–1.42]
	former smoker	1.07 [0.87–1.33]	1.11 [0.66–1.85]	1.11 [0.99–1.25]	0.94 [0.59–1.49]	1.08 [0.92–1.27]
Weight (BMI)	normal	ref.	ref.	ref.	ref.	ref.
	overweight	1.01 [0.89–1.14]	1.02 [0.76–1.39]	1.07 [0.99–1.14]	1.10 [0.84–1.45]	1.04 [0.95–1.15]
	obese	1.05 [0.91–1.21]	1.08 [0.77–1.51]	1.13 [1.05–1.23]	0.89 [0.66–1.21]	1.05 [0.94–1.17]
	underweight	1.16 [0.83–1.62]	1.93 [0.88–4.25]	1.24 [1.03–1.49]	1.57 [0.78–3.19]	1.65 [1.28–2.13]
Comorbidity count >3		1.29 [1.16–1.43]	1.76 [1.37–2.26]	1.29 [1.22–1.37]	1.43 [1.13–1.80]	1.49 [1.37–1.61]
Years since COPD diagnosis		1.00 [1.00–1.01]	0.99 [0.97–1.01]	1.00 [1.00–1.01]	1.00 [0.98–1.02]	1.00 [0.99–1.00]
Presence of cough		1.01 [0.88–1.15]	0.94 [0.69–1.27]	0.98 [0.91–1.06]	0.88 [0.66–1.16]	0.99 [0.89–1.09]
Presence of sputum production		1.12 [0.98–1.28]	0.97 [0.72–1.31]	1.04 [0.97–1.13]	1.23 [0.93–1.63]	1.02 [0.92–1.12]
Presence of dyspnea		1.11 [0.99–1.24]	1.50 [1.14–1.98]	1.24 [1.16–1.32]	1.33 [1.05–1.69]	1.30 [1.19–1.41]
Exacerbation history	no exacerbations	ref.	ref.	ref.	ref.	ref.
	mild exacerbations	1.14 [0.89–1.46]	0.89 [0.50–1.59]	1.14 [1.00–1.31]	0.84 [0.49–1.43]	1.08 [0.89–1.30]
	moderate exacerbations	1.13 [1.00–1.28]	1.42 [1.05–1.91]	1.09 [1.01–1.16]	1.23 [0.93–1.62]	1.22 [1.11–1.34]
	severe exacerbations	1.19 [1.03–1.38]	2.57 [1.81–3.64]	1.26 [1.16–1.37]	1.56 [1.13–2.16]	1.73 [1.55–1.93]
Goodness of fit	Scaled Deviance	1.1997	1.5600	1.0765	1.5102	1.1218

Notes: Estimates with p<0.05 are printed in bold. ^aIncludes general practitioner, specialist, and outpatient hospital care. ^bIncludes rehabilitation and physiotherapy costs.

Table 4 Predictors of changes in annual direct costs after 18 months (in €)

Covariate		Outpatient costs^a	Inpatient costs	Medication costs	Other costs^b	Total direct costs
Intercept		229 [55 to 403]	−677 [−2,043 to 688]	175 [−167 to 516]	105 [−183 to 392]	515 [−1,236 to 2,267]
COPD GOLD	grade 1	ref.	ref.	ref.	ref.	ref.
	grade 2	−6 [−100 to 89]	602 [−149 to 1,353]	42 [−144 to 228]	138 [−22 to 297]	930 [−40 to 1,899]
	grade 3	−19 [−120 to 82]	584 [−214 to 1382]	33 [−165 to 231]	54 [−116 to 224]	813 [−213 to 1,838]
	grade 4	−65 [−201 to 71]	2031 [948 to 3,114]	37 [−229 to 302]	264 [34 to 494]	2346 [960 to 3,732]
	grade unclassified	34 [−73 to 141]	503 [−348 to 1,354]	54 [−159 to 267]	166 [−15 to 348]	689 [−420 to 1,797]
Age (years)	<55	ref.	ref.	ref.	ref.	ref.
	55–64	34 [−58 to 126]	692 [−33 to 1,416]	−48 [−230 to 134]	3 [−151 to 157]	468 [−4,845 to 1421]
	65–74	33 [−59 to 125]	1,188 [461 to 1,915]	1 [−181 to 184]	51 [−104 to 205]	1,018 [66 to 1,969]
	>74	55 [−61 to 171]	902 [−17 to 1820]	36 [−192 to 265]	−15 [−209 to 180]	791 [−402 to 1,983]
Sex	male	ref.	ref.	ref.	ref.	ref.
	female	8 [−47 to 62]	−335 [−771 to 100]	−39 [−146 to 68]	121 [29–214]	−153 [−714 to 408]
Education	basic	ref.	ref.	ref.	ref.	ref.
	secondary	80 [20 to 140]	81 [−395 to 556]	−11 [−128 to 105]	−14 [−115 to 88]	150 [−461 to 762]
	higher	−10 [−82 to 61]	−528 [−1,094 to 38]	−37 [−177 to 103]	14 [−106 to 134]	−608 [−1,336 to 120]
Smoking status	never smoker	ref.	ref.	ref.	ref.	ref.
	smoker	6 [−110 to 122]	942 [20 to 1,863]	112 [−113 to 337]	−47 [−240 to 147]	937 [−237 to 2,110]
	former smoker	26 [−80 to 132]	222 [−623 to 1,068]	118 [−87 to 323]	−53 [−230 to 123]	312 [−757 to 1,380]
Weight (BMI)	normal	ref.	ref.	ref.	ref.	ref.
	overweight	15 [−47 to 77]	99 [−392 to 591]	11 [−111 to 132]	42 [−62 to 147]	176 [−458 to 811]
	obese	19 [−51 to 89]	−91 [−645 to 463]	70 [−66 to 206]	−63 [−181 to 56]	−54 [−768 to 660]
	underweight	74 [−89 to 237]	1978 [691 to 3266]	294 [−27 to 615]	137 [−138 to 412]	3679 [1,978 to 5,380]
Comorbidity count >3		107 [53 to 161]	835 [412 to 1,257]	187 [82 to 292]	136 [47 to 225]	1,579 [1,029 to 2,129]
Years since COPD diagnosis		2 [−2 to 6]	−9 [−40 to 23]	−3 [−11 to 4]	1 [−6 to 8]	−8 [−48 to 32]
Presence of cough		17 [−51 to 84]	−192 [−724 to 340]	−30 [−161 to 101]	−77 [−190 to 36]	−217 [−901 to 467]
Presence of sputum production		58 [−9 to 125]	−118 [−644 to 408]	35 [−94 to 165]	82 [−30 to 194]	2 [−676 to 679]
Presence of dyspnea		48 [−10 to 106]	839 [380 to 1,299]	174 [60 to 287]	100 [3 to 198]	1,131 [538 to 1,724]
Exacerbation history	no exacerbation	ref.	ref.	ref.	ref.	ref.
	mild exacerbation	33 [−89 to 155]	51 [−923 to 1,025]	−12 [−250 to 226]	−139 [−348 to 70]	171 [−1,100 to 1,441]
	moderate exacerbation	83 [21 to 144]	595 [107 to 1,082]	−54 [−174 to 67]	75 [−29 to 179]	887 [258 to 1,516]
	severe exacerbation	76 [2 to 150]	1,779 [1,098 to 2,460]	61 [−84 to 206]	214 [88 to 339]	1,425 [577 to 2273]
Direct costs at baseline^c		−704 [−747 to −661]	−821 [−884 to −757]	−126 [−175 to −78]	−920 [−965 to −876]	−669 [−727 to −611]
Goodness of fit	Scaled Deviance	1.0140	1.0141	1.0143	1.0146	1.0153

Notes: Estimates with p<0.05 are printed in bold. ^aIncludes general practitioner, specialist, and outpatient hospital care. ^bIncludes rehabilitation and physiotherapy costs. ^cDirect costs at baseline per €1,000.

Table 5 Baseline comparison of demographics and disease status, patients present for both visits (study participants) vs patients lost to follow-up (baseline only)

	Study participants with follow-up (n=1904)	Baseline only (n=667)	p-value
% grade unclassified	15.9	17.1	<0.0001^a
% GOLD grade 1	8.9	4.4
% GOLD grade 2	38.0	28.5
% GOLD grade 3	30.0	36.4
% GOLD grade 4	7.1	13.5
Age (years)	65.1 (8.1)	66.0 (9.2)	0.0262^b
% Males	59.5	58.9	0.8094^a
% Basic school education	55.7	59.1	0.1492^a
% Secondary school education	27.2	23.4
% Higher school education	17.1	17.5
FEV1/FVC	56.1 (13.5)	54.5 (14.5)	0.0130^b
% Never smoker	7.0	6.0	0.0818^a
% Former smoker	68.3	65.1
% Current smoker	24.7	28.9
BMI (kg/m^2)	27.2 (5.2)	27.1 (6.0)	0.5464^b
% Underweight (BMI <18.5)	2.6	5.1	0.0198^a
% Normal weight (18.5≤ BMI <25)	34.1	33.4
% Overweight (25≤ BMI <30)	36.5	36.4
% Obese (BMI ≥30)	26.8	25.0
% No exacerbation	48.2	42.7	0.0012^a
% Mild exacerbation	4.8	5.4
% Moderate exacerbation	29.4	27.5
% Severe exacerbation	17.6	24.4
% with presence of cough	44.5	50.6	0.0065^a
% with presence of sputum production	45.8	51.4	0.0137^a
% with presence of dyspnea	41.2	59.3	<0.0001^a
Number of comorbidities	3.9 (2.6)	3.8 (2.8)	0.3424^c
SGRQ^d	40.7 (19.4)	48.3 (21.1)	0.0001^b
Total direct costs^e	6,739 (8,628)	8,657 (12,789)	0.0002

Notes: Data are mean (standard deviation) or percentage. Means and percentages relate to participants with valid data for that particular variable. ^ap-value based on Chi² test. ^bp-value based on t-test. ^cp-value based on Mann-Whitney U test. ^dScoring ranges from 0 to 100, with higher scores indicating worse HRQoL. ^eIncludes rehabilitation and physiotherapy costs, in addition to outpatient, inpatient and medication costs.

Table 6 Determinants of future costs and cost increases calculated with Inverse Probability Weighting to adjust for dropout bias

		Future costs (Table 3) – Gamma regression model	Cost increases (Table 4) – Change Score model
		Total Direct costs	Total Direct costs
Intercept		2,400 [1,829 to 3,150]	660 [−1,131 to 2,451]
COPD GOLD	grade 1	ref.	ref.
	grade 2	1.23 [1.05 to 1.43]	923 [−116 to 1,961]
	grade 3	1.25 [1.07 to 1.47]	788 [−298 to 1,873]
	grade 4	1.57 [1.28 to 1.93]	2,384 [986 to 3,781]
	grade unclassified	1.13 [0.95 to 1.34]	753 [−409 to 1,914]
Age (years)	<55	ref.	ref.
	55–64	1.08 [0.94 to 1.24]	424 [−522 to 1,370]
	65–74	1.22 [1.06 to 1.40]	929 [−14 to 1,873]
	>74	1.16 [0.98 to 1.38]	621 [−545 to 1,786]
Sex	male	ref.	ref.
	female	0.95 [0.87 to 1.03]	−161 [−728 to 407]
Education	basic	ref.	ref.
	secondary	1.03 [0.94 to 1.13]	147 [−478 to 772]
	higher	0.89 [0.80 to 0.99]	−638 [−1,373 to 96]
Smoking status	never smoker	ref.	ref.
	smoker	1.17 [0.98 to 1.39]	810 [−374 to 1,993]
	former smoker	1.08 [0.92 to 1.26]	283 [−799 to 1,365]
Weight (BMI)	normal	ref.	ref.
	overweight	1.05 [0.95 to 1.15]	237 [−408 to 881]
	obese	1.05 [0.94 to 1.17]	−35 [−762 to 692]
	underweight	1.69 [1.33 to 2.15]	4005 [2,365 to 5,645]
Comorbidity count >3		1.48 [1.36 to 1.60]	1589 [1,031 to 2,147]
Years since COPD diagnosis		1.00 [0.99 to 1.00]	−7 [−48 to 34]
Presence of cough		0.98 [0.89 to 1.09]	−290 [−984 to 403]
Presence of sputum production		1.02 [0.92 to 1.12]	39 [−648 to 726]
Presence of dyspnea		1.30 [1.19 to 1.42]	1,174 [572 to 1776]
Exacerbation history	no exacerbation	ref.	ref.
	mild exacerbation	1.08 [0.90 to 1.29]	142 [−1,126 to 1,411]
	moderate exacerbation	1.23 [1.12 to 1.35]	941 [299 to 1583]
	severe exacerbation	1.73 [1.55 to 1.93]	1,531 [685 to 2377]
Direct costs at baseline^a		-	−681 [−740 to −623]
Goodness of fit	Scaled Deviance	1.1230	1.0154

Notes: Estimates with p<0.05 are printed in bold. ^aDirect costs at baseline per €1,000. Inverse Probability Weights were calculated based on the probability of participating in the follow-up. Weights ranged between 1.07 and 2.52 and the sum of weights was 2408, imitating the cohort at baseline.

Data Availability

The full dataset supporting the conclusions of this article is available upon request and application from the Competence Network Asthma and COPD (ASCONET, http://www.asconet.net/html/cosyconet/projects).